Better than Firefox's built-in backup, but unnecessarily complicated!
I don't see the point of many of the features. Unfortunately, there's no help section to clarify this.

From the volume of open issues and the lack of activity on Git, It looks like Sienori has either abandoned this extension or doesn't have the time to maintain it. April 26.

Auto-save doesn't work, hence data loss

For years, this add-on has suffered from a persistent bug: after an unknown background action, the "Open" button in the Saved Sessions Manager suddenly stops working. I’ve spent several hours troubleshooting, but the technical root cause remains elusive.

Here is what I have established so far:

Profile Corruption: Something is corrupting the user profile. Creating a fresh profile resolves the issue, but only temporarily.

No Add-on Conflicts: I have 100% ruled out conflicts with other extensions.

Clean Install: The issue is not caused by leftover data; a full, clean re-installation of Firefox did not fix it.

The most important point: While I cannot pinpoint the exact trigger in the code, I am able to reproduce the bug reliably. I am happy to assist with further questions or testing.

I normally really like and enjoy this add-on, but there is a horrible bug, which from time to time deletes all sessions and lefts a blank session manager. I dont know if it has to do with updates or something like that. But just today after a long time not saving my sessions in a separate file they are gone.

saved my 3k tabs session

It used to work fine on Firefox mac, now nothing happens when you click OPEN or OPEN IN NEW WINDOW.

Hopefully, it will get fixed soon.

Fundamentally useless. 'Open' button for saved tabs cannot be coaxed to work, at all. F$^# this piece of s#$^%.

It prevents the device from receiving tabs that were shared with it... other than that, I like it, but that feature is more important than this add-on.

It's highly customizable, and it works exactly as I want it to.

Works well for me so far.
Please add support for local PDFs, so they can be reopened when restarting the browser.

I am a paid user of other browsers. I tried the Firefox version, but I encountered a few frustrating points. For example, when restoring a session at startup, the window shifts slightly to the left. It would also be nice if it supported title-changing extensions like Window Titler, but this might be unavoidable until Firefox officially supports it.

I hope for future improvements!

Almost does the job, but tab groups are destroyed, as others have mentioned.

Firefox closed all my tabs without warning and couldn't restore them from its own session backup files, even though those files contained all my tabs. This extension helped me restore them all easily, which saved me from having to restore a large number of tabs manually, one by one.
If this extension wasn't there, I would have replaced Firefox with another browser.